The present disclosure may provide imaging method and system. The method may include obtaining a plurality of signals relating to a region of interest (ROI) of an object acquired by applying to the object a plurality of chemical exchange and saturation transfer (CEST) preparations with a plurality of offset frequencies; and generating an image of the ROI based on the plurality of signals. The plurality of CEST preparations may be configured to excite proton exchange of a substance in the ROI. The plurality of CEST preparations may be divided into one or more groups. Each of the one or more groups may include multiple CEST preparations with a same offset frequency among the plurality of offset frequencies. After a last CEST preparation in each of the one or more groups is applied to the object, the substance may reach a saturation degree that exceeds a saturation threshold.